Well, there are two kinds of drunk talks. You get the first one, when you are simply very drunk at the tavern(buy a couple of drinks and find out). The second one, with sex, starts via player-initiated dialogue(let us drink and make love tonight, for tomorrow we may be dead), after all 15 regular talks have triggered. It will lead to sex only if you 1) offer him a drink; 2) offer strong wine instead of regular one; 3) before the conversation, wear some equipment or use spells that give you a CHA of 18 or more(or if your natural CHA is 18+) - then you'll get him to sleep with you, get the morning-after talk and get an additional player-initiated option afterwards.
With breakup-related stuff, let me see: Aerie, Anomen, Edwin, Imoen, Jaheira, Korgan, Minsc, Viconia.
Aaand with spirit stuff, it's been quite a while, but I think it's this - for someone like Xan, seeing his elven beloved without her spirit is like seeing a zombie - he's scared out of his wits, and, coupled with the legends of the Bhaalspawn and with the Slayer(not to mention sleep-deprivation), he's starting to slip, and to be really afraid to wake up next to a real monster. Worst of all is, Xan used to feel elven Charname thourgh the Spirit before she lost her soul, just as he'd feel Kivan or his elven friends from Evereska: Xan would know their mood, or their "level of goodness"
, or their intention. Xan used to rely on their communion, on this close connection - but now there's nothing, darkness, a blank wall, and it terrifies him. So in his darkest moments, he may well assume the worst.
(Not to mention that privately, I think that if there was an opportunity to kill someone and to steal someone's spirit so that Charname would live, I think Xan would come very close to doing it, to save her).